The present invention relates to a resin composition for welding having high mechanical strength, impact resistance, heat resistance and chemical resistance as well as excellent weld strength and stability, which composition can be utilized as industrial material in the various fields of industry such as electric and electronic field and automobile field. The present invention also relates to moldings and a secondary battery container using the said resin composition.
Since polyphenylene ether resins are excellent in mechanical strength, heat resistance, electrical properties and dimensional stability, they are used for a variety of industrial products such as electric and electronic parts, OA equipment parts and automobile parts. These resins, however, have the disadvantage of being poor in chemical resistance because they are amorphous resins, so that they are hardly available for applications where oils or chemicals are likely to contact to the product.
On the other hand, polypropylene resins are inexpensive and lightweight and also excel in moldability and chemical resistance, so that they are used very widely for a variety of industrial products such as automobile-related parts like bumper, sheets, films, etc. These resins, however, are inferior to polyphenylene ether resins in the aspect of mechanical strength and heat resistance.
So, there has been proposed a polyblend which combines the advantages of the said two types of resin, namely a composition which possesses both of the toughness and heat resistance of polyphenylene ether resins and the heat resistance of polypropylene resins.
For example, U.S. Pat. No. 3,361,851 teaches that a composition with excellent chemical resistance can be obtained by blending a polyphenylene ether and a polyolefin resin. Also, Japanese Patent Application Laid-Open (KOKAI) Nos. 63-113058 and 2-305814 teach that the compatibility of polyphenylene ether resins and polyolefin resins can be improved by adding a hydrogenated block copolymer to a composition comprising the said two types of resin.
Capitalizing on these advantages of a blend of a polyphenylene ether resin and a polypropylene resin, Japanese Patent Application Laid-Open (KOKAI) Nos. 8-195188 and 9-120801 propose application of such a resin blend for the molding of a closed battery container. This proposal is intended to improve mechanical strength and heat resistance by the blending of a polyphenylene ether resin while securing chemical resistance and vapor barrier properties provided by the polypropylene resin. Indeed, these techniques make it possible to obtain chemical resistance, mechanical strength and heat resistance that could never be obtained by single use of a conventional polypropylene resin or polyphenylene ether resin.
However, with commercialization of electric cars in recent years, stricter requirements are demanded at the closed type secondary batteries used for such electric cars. Specifically, requirement for higher pressure resistance at high temperatures is imminent in the face of the necessity for the rise of working temperature and internal pressure which is essential for producing higher power.
In use of a polyphenylene ether/polypropylene resin blend for manufacturing a pressure vessel such as a secondary battery container, the method of closing the vessel is an important factor. Usually, welding is used for joining the vessel body and the cover for closing the vessel because of the simplicity of the operation. As examples of the method of welding, there are used xe2x80x9chot plate weldingxe2x80x9d in which the resin parts to be welded are brought into contact with a heated plate to fuse the surfaces of the resin part to thereby effect desired welding, xe2x80x9cvibration weldingxe2x80x9d which comprises fusing the surfaces of the resin part by means of vibration, and xe2x80x9cultrasonic weldingxe2x80x9d according to which surface fusion is effected by the application of ultrasonic waves. However, when using a conventional polyphenylene ether/polypropylene resin blend, the weld strength provided by these welding means is low and the problem is pointed out that the weld zone may be forced to come off when an internal pressure is exerted thereto. Especially, there is a wide scatter of weld strength, posing a serious problem in practical use of the blend.
As a result of the present inventors"" earnest studies to solve the above problem, it has been found that a resin composition comprising a block copolymer of a polyphenylene ether resin and a crystalline polypropylene resin and having a specific structural form has excellent mechanical strength, heat resistance, impact resistance and chemical resistance as well as high weld strength and stability.
The present invention has been attained on the basis of the above finding.
The object of present invention is to providing a resin composition suited for welding having excellent mechanical strength, heat resistance, impact resistance and chemical resistance and capable of providing high weld strength with good stability.
The other object of the present invention is to provide resin moldings and a secondary battery container produced from the said resin composition by making the best use of its advantageous properties mentioned above.
To attain the above aim, in the first aspect of the present invention, there is provided a resin composition comprising 5 to 60 parts by weight of a polyphenylene ether resin and 40 to 95 parts by weight of a crystalline polypropylene resin, and further containing a hydrogenation product of an aromatic vinyl compound-conjugated diene copolymer in an amount of 1 to 30 parts by weight based on 100 parts by weight of said polyphenylene ether resin and crystalline polypropylene resin combined, said crystalline polypropylene resin forming a continuous phase while said polyphenylene ether resin forming a disperse phase, the ratio of the weighted average inter-particle-wall distance (Lw) to the added average inter-particle-wall distance (Ln) of said disperse phase, Lw/Ln, being 1.0 to 3.0.
In the second aspect of the present invention, there is provided a resin molding comprising the resin composition as defined in the first aspect.
In the third aspect of the present invention, there is provided a secondary battery container comprising the resin composition as defined in the first aspect.